Technology
Light emitting diodes (LEDs) create light by combining electrons and holes in semiconductor materials. LEDs are incorporated into a broad range of general lighting applications and electronic devices. Testing the quality of exciting materials and developing new efficient materials for LEDs and display systems will continue to be important as LEDs are incorporated into additional products. Research at Bowling Green State University has led to the development of a spectrometer and associated method to characterize charge carriers in luminescent semiconductors and measure their ionization energies.
Measurement of ionization energies is critical in the design of optoelectronics and many semiconductor devices. The novel spectrometer and method are based on a thermally stimulated luminescence-based approach to measure the donor ionization energy. The approach has been demonstrated through the measurement of donor ionization energies in chemical vapor transport grown single crystals of zinc oxide.
The prototype system is easily fabricated, scalable, and compact. The system could be used in measuring donor energies in luminescent semiconductors and in thin films on conductive substrates.
Competitive Advantages
Current approaches to characterizing charge carriers and measuring ionization energies in luminescent semiconductors generally involve temperature dependent Hall-effect measurements. Unlike Hall-effect systems that are costly, the developed system is inexpensive and could be fabricated at a fraction of the cost of other systems. In addition, the method is a relatively simple technique that provides direct donor characterization and the sample shape or thickness uniformity of the semiconductor measured does not impact the measurement. More importantly, characterizing charge carriers in thin films on conductive layers is currently not feasible with the Hall-effect method because the applied current diffuses into the conductive layers and interferes with the measurements of the film.
Opportunity
The spectrometer and associated method of characterizing charge carriers in luminescent semiconductors would be useful in both testing the quality of exciting materials and developing new efficient materials for LEDs and display systems. The global LED lighting market is an attractive market that is expected to increase to over $42 billion by 2020. Growth in the market is fueled by decreasing cost, longer life span and higher efficiency LED lamps along with growing demand in newer applications.